The present invention concerns a regulable hydraulic dashpot for motor vehicles.
German OS 4 041 829 A1 discloses a regulable single-cylinder dashpot. A valve on the wall of the shock-absorption cylinder allows multiple-level adjustment of the shock-absorption force by way of a bypass around a throttle valve on the shock-absorption piston. The bypass is a cylindrical component mounted on the cylinder or integrated into it in the form of an extruded section. The bypass is sealed off between its two hydraulic-fluid conveying connections. Each fluid-conveying connection communicates with one of the displacement chambers inside the dashpot.
Another approach to establishing a bypass that communicates with the chambers is known from German OS 3 831 718 A1. The shock-absorption cylinder is accommodated in a cylindrical container. The end of the cylinder that accommodates the gas chamber rests tight against it. A piston-rod centering cap is mounted over both at the other end. The resulting hydraulic-fluid channel around the cylinder and between the chambers is divided into an upper and a lower influent channel. A shock-absorption performance-curve selection valve provides communication between one of the hydraulic-fluid conveying connections and the upper influent channel and between the other hydraulic-fluid conveying connection and the lower influent channel. Since the fluid channel is demarcated by a double-walled cylinder, the gas-filled pressure-compensation can be smaller or the overall dashpot wider.
German GM 9 210 834 describes a regulable single-cylinder dashpot with a shock-absorption performance-curve selection valve mounted on the cylinder. The cylinder is divided into two parts, leaving a bypass between the displacement chambers. One part includes a narrower section as long as the length of the stroke traveled by the piston. The other part overlaps the narrower section. The ends of the cylinder's parts are open and the two parts are sealed off from each other. The shock-absorption performance-curve selection valve is mounted on the cylinder such that one hydraulic-fluid conveying connection communicates with an annular hydraulic-fluid channel that communicates in turn with the upper displacement chamber and the other fluid-conveying connection opens directly into the lower displacement chamber.
Such a shock-absorption cylinder has several joints that must be welded or soldered and is accordingly complicated to manufacture. Another drawback is that the design of the hydraulic-fluid channel dictates the position of the shock-absorption performance-curve selection valve hydraulic-fluid conveying connections and accordingly the axial position of the valve and allows no variability.